The intent of this proposal is to develop a surgical tool that can be used to study surgery performed on patients with cerebral palsy (CP) and to study the mechanical and biological properties of spastic skeletal muscle. CP is a neuromuscular disorder that can result in joint contractures that require surgical correction. Surgical procedures used include tendon lengthenings and tendon transfers. While a great deal of progress has been made creating procedures that improve function, comparatively little attention has been directed toward objectively evaluating such procedures. In order to critically differentiate between the various surgical procedures available to correct ankle deformities, it is suggested that an understanding of the effects of the surgery on muscle must be defined and functional differences between procedures (if any) documented. The investigators also propose quantitative studies of the passive mechanical properties of spastic skeletal muscle to determine the relationship between passive tension (easily measured intraoperatively) and optimal sarcomere length (measured with a laser diffraction tool). They thus propose development and testing of an intraoperative laser diffraction device for sarcomere length measurement that allows muscle properties to be defined during surgical tendon lengthening, such as is commonly performed on patients with CP. In the first phase of the study, a user-friendly intraoperative laser diffraction device will be fabricated based on a design which has been used for over 15 years in this laboratory. This device will then be used in a prospective clinical study which compares two methods for equinus deformity correction: tendoachilles lengthening (TAL) and gastrocnemius-soleus recession (GSR, "Strayer" procedure). Intraoperative laser diffraction will be used during surgical correction as an objective measure of the biomechanical effects of the surgery. Functional differences (if any) between the TAL and GSR procedures will be evaluated by comparing kinetic and kinematic analysis of normal gait in these subjects before and after surgery. They will also completely characterize the spastic muscle in terms of the titin isoforms expressed and determine the degree to which these isoforms affect passive mechanical properties. Muscle fibers will be typed based on the myosin heavy chain expressed. These data, in conjunction with intraoperative sarcomere lengths will be integrated into a biomechanical model that includes muscle, tendon and joint properties and can be used to predict joint function given muscle properties. The goal is to gain understanding of the immediate intraoperative and functional postoperative effects of these very common surgical procedures. In addition, these data will be relevant to management of other disorders such as stroke, head injury and spinal cord injury, where surgical tendon transfers are performed.